Currently, as a raw material of a commercial silane-based coating agent, a trifunctional silane is mainly used, and a polysiloxane having moderate hardness and flexibility is formed by such a trifunctional silane. However, the hard coating properties of a film of a trifunctional silane are not sufficient. Therefore, the trifunctional silane is mixed with a tetrafunctional silane and colloidal silica to compensate for the hard coating properties. But, a problem is that if the film is hardened, the film cracks easily, and the adhesiveness worsens.
Silane-based coating agents include antifouling film-forming compositions containing a trifunctional alkoxysilane compound having an epoxy group (for example, see Patent Document 1). In addition, silane-based coating agents containing a photocatalyst are also proposed, and the film is cured using a photo-acid-generating agent, a crosslinking agent, a curing catalyst, or the like (for example, see Patent Documents 2 and 3). Further, silane-based organic-inorganic complex gradient materials having a component gradient structure in which the content of the metal-based compound in the material changes continuously in the depth direction from the surface of the material are also proposed (for example, see Patent Document 4).
The inventors have provided an organic-inorganic complex in which the surface has very high hardness and the inside and the back surface side have appropriate hardness and which has excellent adhesiveness to a substrate, by irradiating an organic silicon compound with ultraviolet rays in the presence of a photosensitive compound (see Patent Document 5). However, a further improvement has been desired in adhesiveness to a base material and moisture resistance.
On the other hand, for hard coating films, the use of acrylate-based resins or the like as UV-curable resins is known. For example, Patent Document 6 describes a hard coating film containing a (meth)acrylate mixture (A), a photopolymerization initiator (B), an ethylenic unsaturated group-containing urethane oligomer (C), a colloidal silica sol (D), and a diluent (E), and describes that the obtained film has good pencil hardness, curl, and adhesiveness to a base material.
In addition, Patent Document 7 describes the use of a curable composition containing (A) particles obtained by bonding particles of an oxide of at least one element selected from the group consisting of silicon, aluminum, zirconium, titanium, zinc, germanium, indium, tin, antimony, and cerium to an organic compound comprising a polymerizable unsaturated group, (B) a compound having a urethane bond and two or more polymerizable unsaturated groups in the molecule, and (C) a photopolymerization initiator, and describes that the curable composition has excellent coating properties and can form on the surfaces of various base materials a coating film (coating) having high hardness and a high refractive index and having excellent abrasion resistance and excellent adhesiveness to base materials and low refractive index layers.
Further, Patent Document 8 describes an ultraviolet-curable hard coating resin composition obtained by blending (A) a mixture of a hydrolysate of an organic silicon compound and metal oxide fine particles, (B) a polyfunctional acrylate or methacrylate, and (C) a photopolymerization initiator, and describes that the bleeding of the antistatic agent on the surface, a decrease in transparency, a deterioration in moisture resistance, and the like can be kept within practically allowable ranges, and functions (abrasion resistance, surface hardness, moisture resistance, solvent and chemical resistance, and the like) as a hard coating are satisfied.
However, these hard coating films using acrylate-based resins and the like have poorer wear resistance than inorganic films, and therefore, a metal oxide sol having high hardness is added for improvement. But, in this method, the surfaces of the metal oxide particles are covered with a large amount of the resin, and a sufficient effect cannot always be expected. Particularly, in the case of anti-Newton ring films that contain metal oxide particles having a large particle diameter to form unevenness on the surfaces of the films, a problem is that unless the surfaces of the metal oxide particles are covered with the resin, the metal oxide particles having a large particle diameter fall off in a wear test.
For these problems, the inventors have already found that an organic-inorganic complex in which the surface has very high hardness and which has excellent adhesiveness to a substrate and excellent moisture resistance can be produced by blending an ultraviolet-curable compound into a polysiloxane-based organic-inorganic complex (Patent Document 9). However, the light reflection properties of the above organic-inorganic complex have not been studied.
Therefore, the inventors have developed an organic-inorganic complex in which the ten-point average roughness of the organic-inorganic complex surface is 0.1 μm to 5 μm by using metal oxide particles having a primary particle diameter of 0.05 μm to 0.2 μm (Patent Document 10). The performance as an anti-Newton ring film has been sufficient, but the new problem of an increase in haze factor has arisen by providing unevenness by the particles having a large particle diameter.